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<h1>navo/algorithm/hash/signature/crc16.c</h1>  </div>
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<a href="crc16_8c.html">浏览该文件的文档。</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */</span>
<a name="l00011"></a>00011 <span class="preprocessor">#ifdef _MSC_VER</span>
<a name="l00012"></a>00012 <span class="preprocessor"></span><span class="preprocessor">#pragma optimize(&quot;t&quot;, on)</span>
<a name="l00013"></a>00013 <span class="preprocessor"></span><span class="preprocessor">#endif  </span><span class="comment">/* #ifdef _MSC_VER */</span>
<a name="l00014"></a>00014 
<a name="l00015"></a>00015 <span class="preprocessor">#include &quot;<a class="code" href="crc16_8h.html" title="Definitions and declarations for 16 bit CRC.">crc16.h</a>&quot;</span>
<a name="l00016"></a>00016 
<a name="l00017"></a>00017 <span class="preprocessor">#ifdef __cplusplus</span>
<a name="l00018"></a>00018 <span class="preprocessor"></span><span class="keyword">extern</span> <span class="stringliteral">&quot;C&quot;</span> {
<a name="l00019"></a>00019 <span class="preprocessor">#endif </span><span class="comment">/* #ifdef __cplusplus */</span>
<a name="l00020"></a>00020 
<a name="l00021"></a><a class="code" href="group__CRC-16.html#ga5ad218af978eb0211e524ee4258d965a">00021</a> NV_IMPL <span class="keywordtype">void</span> <a class="code" href="group__CRC-16.html#ga5ad218af978eb0211e524ee4258d965a" title="建立CRC码表">crc16_build</a>(uint16_t* buf, uint16_t poly)
<a name="l00022"></a>00022 {
<a name="l00023"></a>00023     uint16_t i, j, v;
<a name="l00024"></a>00024 
<a name="l00025"></a>00025     poly = __le16_to_cpu(poly);
<a name="l00026"></a>00026     <span class="keywordflow">for</span> (j = 0; j &lt; CRC16_TBL_SIZE; buf[j++] = v) {
<a name="l00027"></a>00027         v = j &lt;&lt; 8;
<a name="l00028"></a>00028         <span class="keywordflow">for</span> (i = 0; i++ &lt; 8;) {
<a name="l00029"></a>00029             <span class="keywordflow">if</span> (v &amp; 0x8000) {
<a name="l00030"></a>00030                 v &lt;&lt;= 1;
<a name="l00031"></a>00031                 v ^= poly;
<a name="l00032"></a>00032             } <span class="keywordflow">else</span>
<a name="l00033"></a>00033                 v &lt;&lt;= 1;
<a name="l00034"></a>00034         }
<a name="l00035"></a>00035     }
<a name="l00036"></a>00036 }
<a name="l00037"></a>00037 
<a name="l00038"></a>00038 NV_IMPL <span class="keywordtype">void</span> __crc16_process(<a class="code" href="structcrc16__ctx.html" title="CRC-16上下文">crc16_ctx</a>* ctx, <a class="code" href="group___xE6_x95_xB4_xE5_x9E_x8B_xE5_xAE_x9A_xE4_xB9_x89.html#gae1affc9ca37cfb624959c866a73f83c2" title="8比特无符号整型">uint8_t</a>* buf, <span class="keywordtype">size_t</span> cnt)
<a name="l00039"></a>00039 {
<a name="l00040"></a>00040     <span class="keywordtype">int</span> i;
<a name="l00041"></a>00041     uint16_t poly = ctx-&gt;<a class="code" href="structcrc16__ctx.html#afb251be1f98631b42a1e3ae1e8199d61" title="多项式">poly</a>;
<a name="l00042"></a>00042     uint16_t crc = ctx-&gt;<a class="code" href="structcrc16__ctx.html#aa60093a9a5d5d17864cfda66c47733e3">crc</a>;
<a name="l00043"></a>00043 
<a name="l00044"></a>00044     <span class="keywordflow">while</span> (cnt--) {
<a name="l00045"></a>00045         crc ^= (*buf++ &lt;&lt; 8);
<a name="l00046"></a>00046         <span class="keywordflow">for</span> (i = 0; i++ &lt; 8;) {
<a name="l00047"></a>00047             <span class="keywordflow">if</span> (crc &amp; 0x8000) {
<a name="l00048"></a>00048                 crc &lt;&lt;= 1;
<a name="l00049"></a>00049                 crc ^= poly;
<a name="l00050"></a>00050             } <span class="keywordflow">else</span>
<a name="l00051"></a>00051                 crc &lt;&lt;= 1;
<a name="l00052"></a>00052         }
<a name="l00053"></a>00053     }
<a name="l00054"></a>00054 
<a name="l00055"></a>00055     ctx-&gt;<a class="code" href="structcrc16__ctx.html#aa60093a9a5d5d17864cfda66c47733e3">crc</a> = crc;
<a name="l00056"></a>00056 }
<a name="l00057"></a>00057 
<a name="l00058"></a>00058 NV_IMPL <span class="keywordtype">void</span> __crc16_update(<a class="code" href="structcrc16__ctx.html" title="CRC-16上下文">crc16_ctx</a>* ctx, <span class="keyword">const</span> uint16_t* tbl,
<a name="l00059"></a>00059                                     <a class="code" href="group___xE6_x95_xB4_xE5_x9E_x8B_xE5_xAE_x9A_xE4_xB9_x89.html#gae1affc9ca37cfb624959c866a73f83c2" title="8比特无符号整型">uint8_t</a>* buf, <span class="keywordtype">size_t</span> cnt)
<a name="l00060"></a>00060 {
<a name="l00061"></a>00061     uint16_t crc = ctx-&gt;<a class="code" href="structcrc16__ctx.html#aa60093a9a5d5d17864cfda66c47733e3">crc</a>;
<a name="l00062"></a>00062 
<a name="l00063"></a>00063     <span class="keywordflow">while</span> (cnt--) {
<a name="l00064"></a>00064         crc = (crc &lt;&lt; 8) ^ tbl[(crc &gt;&gt; 8) ^ *buf++];
<a name="l00065"></a>00065     }
<a name="l00066"></a>00066 
<a name="l00067"></a>00067     ctx-&gt;<a class="code" href="structcrc16__ctx.html#aa60093a9a5d5d17864cfda66c47733e3">crc</a> = crc;
<a name="l00068"></a>00068 }
<a name="l00069"></a>00069 
<a name="l00070"></a><a class="code" href="group__CRC-16.html#gacbb1836c68b56bc083aea965b65cda6a">00070</a> NV_IMPL uint16_t <a class="code" href="group__CRC-16.html#gacbb1836c68b56bc083aea965b65cda6a" title="直接哈希字符串">crc16_hash_nbstr</a>(<span class="keyword">const</span> <span class="keywordtype">char</span>* str, uint16_t* tbl)
<a name="l00071"></a>00071 {
<a name="l00072"></a>00072     uint16_t hash = 0;
<a name="l00073"></a>00073     <a class="code" href="group___xE6_x95_xB4_xE5_x9E_x8B_xE5_xAE_x9A_xE4_xB9_x89.html#gae1affc9ca37cfb624959c866a73f83c2" title="8比特无符号整型">uint8_t</a> ch;
<a name="l00074"></a>00074 
<a name="l00075"></a>00075     <span class="keywordflow">while</span> ((ch = *str++)) {
<a name="l00076"></a>00076         hash = (hash &lt;&lt; 8) ^ tbl[(hash &gt;&gt; 8) ^ ch];
<a name="l00077"></a>00077     }
<a name="l00078"></a>00078 
<a name="l00079"></a>00079     <span class="keywordflow">return</span> __cpu_to_le16(hash);
<a name="l00080"></a>00080 }
<a name="l00081"></a>00081 
<a name="l00082"></a>00082 <span class="preprocessor">#ifdef __cplusplus</span>
<a name="l00083"></a>00083 <span class="preprocessor"></span>}
<a name="l00084"></a>00084 <span class="preprocessor">#endif </span><span class="comment">/* #ifdef __cplusplus */</span>
<a name="l00085"></a>00085 
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